Study On Flow Fluctuation Characteristics Of Spiral Fertilizer Distributor And Optimization Of Key Parameters

As a key core component of fertilization machinery,fertilizer distributor has a significant impact on the efficiency and performance of fertilization machinery.Among them,the spiral fertilizer applicator has the advantages of simple structure,good sealing performance,stable single-turn fertilizer discharge,and low manufacturing cost,and is widely used in fertilization machinery.However,due to the influence of the unique structure of the fertilizer spiral,it is easy to cause the fluctuation of the fertilizer flow.Therefore,this paper simulates the fertilizer discharge process of spiral fertilizer dispenser,explores the law of flow fluctuation and contact force fluctuation of spiral fertilizer dispenser,and on this basis,puts forward the characterization method of axial and circumferential distribution of force chain,and then explores the influence of key parameters of spiral fertilizer dispenser on fertilizer discharge performance,so as to provide guidance for parameter optimization of spiral fertilizer dispenser.The specific research contents and conclusions are as follows:(1)The physical properties of urea particles commonly used in orchards were measured.The results showed that the average length,width and thickness of urea particles were 2.55mm,2.5mm and 2.16mm(length>width>thickness),respectively.The average equivalent diameter is 2.4mm,and the sphericity rate reaches 94.54%.The measured moisture content is 0.82%.The measured density is 1.461g/cm~3.The contact parameters of urea particles are calibrated by discrete element simulation technology.The results show that the dynamic friction coefficient between urea particles and polylactic acid material(PLA)is 0.18,the dynamic friction coefficient between urea fertilizer is 0.1,and the static friction coefficient between urea particles is 0.3,which can provide relevant parameter support for the subsequent simulation model establishment.(2)By using the discrete element method to simulate the fertilizer discharge process of the laboratory-level spiral fertilizer distributor,the law of flow fluctuation and contact force fluctuation between particles is explored.The results show that the reason for the flow fluctuation is that the continuous rotation of the fertilizer discharge spiral causes the periodic change of the opening size between the spiral and the end face of the fertilizer discharge port,which is closely related to the formation and destruction of the force chain between the fertilizer particle systems.There is a one-to-one correspondence between the flow fluctuation and the average normal contact force,that is,the average normal contact force trough corresponds to the flow peak.On this basis,the quantitative indexes of force chain distribution are defined from the axial and circumferential directions,which can lay a theoretical foundation for revealing the flow fluctuation of spiral fertilizer distributor.(3)By using the discrete element method to simulate the fertilizer discharge process of the laboratory-level spiral fertilizer distributor,the influence of key parameters on the internal characteristics of fertilizer particles is explored,and the axial distribution and circumferential distribution of the force chain are analyzed respectively.The results show that the key parameters have a significant effect on the axial and circumferential distribution of the force chain,showing differences in the coefficient of variation and the uniformity index,respectively.In the spiral fertilizer dispenser,the rotational speed,blade diameter and pitch mainly affect the uniformity of fertilizer discharge by the axial distribution of the force chain,and the mathematical model of the coefficient of variation of the uniformity of fertilizer discharge and the axial coefficient of variation of the force chain is established.The rotational speed and pitch are positively correlated,and the blade diameter is negatively correlated,which can provide reference for the parameter optimization of the spiral fertilizer dispenser.(4)The rotational speed,blade diameter and pitch of the spiral fertilizer dispenser were selected to carry out the three-factor and three-level Box-Behnken fertilizer experiment.The artificial neural network prediction model with rotational speed,blade diameter and pitch as input was constructed with the uniformity coefficient of variation as the index.The results showed that the model determination coefficient was 0.99,the average relative error was 2.29%,and the prediction model had good prediction ability.In order to comprehensively consider the efficiency of fertilizer discharge,the effect of fertilizer discharge and the coefficient of variation of fertilizer uniformity,the screw parameter group of fertilizer discharge after neural network optimization is as follows:the rotation speed is 47.6r/min,the leaf diameter is 90mm,the pitch is60mm,the coefficient of variation of fertilizer uniformity is 19.05%,and the fertilizer discharge effect and fertilizer discharge efficiency are better.